kernel->ssa: support string concatenations/interpolations

pkg/compiler/lib/src/ssa/builder_kernel.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
 import '../common/tasks.dart' show CompilerTask;
 import '../compiler.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../io/source_information.dart';
 import '../js_backend/backend.dart' show JavaScriptBackend;
 import '../kernel/kernel.dart';
 import '../tree/dartstring.dart';
 import '../types/masks.dart';
 import '../universe/selector.dart';
 
 import 'graph_builder.dart';
 import 'kernel_ast_adapter.dart';
+import 'kernel_string_builder.dart';
 import 'locals_handler.dart';
 import 'nodes.dart';
 import 'ssa_branch_builder.dart';
 
 class SsaKernelBuilderTask extends CompilerTask {
   final JavaScriptBackend backend;
   final SourceInformationStrategy sourceInformationFactory;
 
   String get name => 'SSA kernel builder';
 
@@ skipping 526 matching lines @@
   @override
   void visitThisExpression(ir.ThisExpression thisExpression) {
     stack.add(localsHandler.readThis());
   }
 
   @override
   void visitNot(ir.Not not) {
     not.operand.accept(this);
     push(new HNot(popBoolified(), backend.boolType));
   }
+
+  @override
+  void visitStringConcatenation(ir.StringConcatenation stringConcat) {
+    KernelStringBuilder stringBuilder = new KernelStringBuilder(this);
+    stringConcat.accept(stringBuilder);
+    stack.add(stringBuilder.result);
+  }
 }